The use of an electric motor to rotate a fan blade to create an airflow has long been known in the art. Although such fans can produce substantial airflow (e.g., 1,000 ft3/minute or more), substantial electrical power is required to operate the motor, and essentially no conditioning of the flowing air occurs.
It is known to provide such fans with a HEPA-compliant filter element to remove particulate matter larger than perhaps 0.3 μm. Unfortunately, the resistance to airflow presented by the filter element may require doubling the electric motor size to maintain a desired level of airflow. Further, HEPA-compliant filter elements are expensive, and can represent a substantial portion of the sale price of a HEPA-compliant filter-fan unit. While such filter-fan units can condition the air by removing large particles, particulate matter small enough to pass through the filter element is not removed, including bacteria, for example.
It is also known in the art to produce an airflow using electro-kinetic techniques, whereby electrical power is converted into a flow of air without utilizing mechanically moving components. One such system is described in U.S. Pat. No. 4,789,801 to Lee (1988), depicted herein in simplified form as FIG. 1A, which is hereby incorporated by reference. System 10 includes an array of first (“emitter”) electrodes or conductive surfaces 20 that are preferably spaced-apart symmetrically from an array of second (“collector”) electrodes or conductive surfaces 30. The positive terminal of a generator such as, for example, pulse generator 40 which outputs a train of high voltage pulses (e.g., 0 to perhaps +5 KV) is coupled to the first array 20, and the negative pulse generator terminal is coupled to the second array 30 in this example.
In another particular embodiment shown herein as FIG. 1B, second electrodes 30 are preferably symmetrical and elongated in cross-section. The elongated trailing edges on the second electrodes 30 are symmetrically and elongated in cross-section. The elongated trailing edges on the second electrodes 30 provide increased area upon which particulate matter 60 entrained in the airflow can attach. While the electrostatic techniques disclosed by the '801 patent are advantageous over conventional electric fan-filter units, further increased air conditioning efficiency would be advantageous. One method of increasing air conditioning efficiency is to position driver electrodes between the collector electrodes whereby the driver electrodes aid in driving the particulates toward the collector electrodes.